An open-rotor type turbine engine mainly comprises, along a longitudinal axis and inside a cylindrical nacelle, supported by the structure of the aircraft (such as the rear portion of the fuselage of an aeroplane), a “gas generator” part and a “thruster” part (only the nacelle part covering the gas generator is fixed, whereas the nacelle parts in which the rotating casings are accommodated are rotational). The thruster part comprises two coaxial and counter-rotating propellers, which are upstream (front) and downstream (rear) respectively and comprise rotational casings having polygonal rings, and which propellers are set into opposite rotation from one another, for example, by a suitable mechanism which is driven by a power turbine which is located at the output of the gas generator part, the blades of the propellers extending radially outside the nacelle.
To allow optimum operation of the turbine engine in the various flight phases encountered, the blades of the counter-rotating propellers can rotate in the radial compartments of the rings. For this purpose, they are set into rotation about their respective pivot axes, by a suitable orientation system for varying the pitch of the blades during flight, that is to say the pitch of the propellers. For example, the blades can vary according to the system, from +90° to 30° for the flight phases, from +30° to −30° for the ground and thrust reversal phases, and can have a rapid return to 90°, in the feathered position, in the event of a malfunction in flight, for which the blades are retracted relative to the direction of travel of the aeroplane and cause as little drag as possible.
As a system for orienting the blades, that described in the French patent application of the applicant FR 11 58891 is known.
A technique allowing optimum lubrication of a bearing, which was developed by the applicant, was the subject matter of FR 12 56140 and consists in channelling the lubricating oil as far as the inside of the bearing, passing through the actuator.